US 3026669 A
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March 27, 1962 R. STANTON 3,026,669
SYNTHETIC ROPE STRUCTURE Filed Aug. 16, 196Q INVENTOR. /6 Raaf/Q7 fA/vro/v F76. 2. BY
MQAWMMJMN ATTO/Q/Viy United States Patent Oiiice 3,02669 Patented Mar. 27, 1962 3,026,669 SYNTHETIC RPE STRUCTURE Robert L. Stanton, Maplewood, NJ., assignor to American Manufacturing Company, luc., Brooklyn, NX., a corporation of Delaware Filed Aug. 16, 1960, Ser. No. 49,866 14 Claims. (Cl. 517-1411) This invention relates to cordage and in particular to an improved rope made of synthetic materials.
Synthetic ropes previously used in maritime industries include all-nylon, all-polypropylene, all-polyethylene and all-polyester fiber types. For many applications, these ropes have proved satisfactory as lthey possess distinct advantages over previous natural fiber type ropes. Notwithstanding some of these advantages, however, their use has also given rise to some disadvantages. For eX- ample, ropes made entirely of commercially available polypropylene have been used by tug boats for towing because they are chemically inert and hence resistant t corrosion, are lighter than natural liber ropes, do not stretch appreciably, are relatively non-absorptive of water, and have high tensile strength. These ropes are generally wound around iXed vertical posts or bitts, on the tugs.
When these yall-polypropylene ropes were placed around the bitts it was found that as the tug boat started to move and the tension on the rope increased, the rope tended to stick momentarily or seized the bitts for a fraction of a second. As the tension increased even more the rope would tend to be dislodged suddenly from the bitt with a consequent jolt which, in some cases, could cause damage to the outside rope yarns in contact with the surf-ace of the bitt.
it is therefore one object of the present invention to provide a novel synthetic rope which is constructed to prevent its sticking to bitts.
Another object of the invention is to provide a novel synthetic rope which is light in weight, water-repellent, buoyant, abrasion-resistant, stable at temperature eX- tremes, possesses high tensile strength, and which does not stick to bitts.
Still another object of `the invention is to provide a strong synthetic maritime towing rope which floats, is chemically inert, water-repellent, has great resistance to abrasion, and has a lower coeicient of friction.
Other objects of the invention may be appreciated upon perusal of the specification, drawings and claims herein.
l have found that the reason for the sticking of the all-polypropylene rope to the bitts is the fact that the pressure and friction on the rope under tension is sufficient to cause its surface to get tacky and thus adhere to the bitts. In accordance with the present invention I therefore provide an improved rope with an inner core of asynthetic material and a layer of yarns surrounding said core which includes yarns of the same synthetic material as the core and also includes yarns of another synthetic material constructed to withstand higher temperatures than said core material. In a preferred form, the outer layer may consist principally of interspersed polypropylene and nylon yarns. Preferably, either the nylon or the polypropylene or both are treated to enhance their heat resistance, abrasion resistance and water resistance.
FIGURE 1 is a side elevation View of a rope constructed according to my invention; and
FIGURE 2 is a simplified enlarged transverse sectional view of the rope of FlG. 1 taken along the line 2 2, shown in FGURE l.
Referring to FIGURES l and 2, a rope indicated generally by the numeral 11 is shown which is constructed according to one form of my invention. Rope 11 may consist, for example, of three single strands 12, 13 and la which have been laid together. As may be seen in FIGURE 2, the single strands 12, 13 and 14 have inner cores 15, 16 and 17 respectively made of polypropylene yarns, that is to say bundles of polypropylene filaments and yarns twisted together. The outer layers 1S, 19 and 20 of the strands 14, 13, and 12 respectively contain yarns 18a, 19a, and 20u of nylon interspersed with yarns 1-8b, 19b and 2Gb of polypropylene. The nylon yarns 1Sa, 19a and 20a have a melting point of 480 F. which is higher than the melting point (330 F.) of the polypropylene yarns 18]?, 1917 and 20h. Consequently, the tendency of the rope 11 to fuse to the bitts is considerably reduced thereby preventing the sudden jolt that formerly occurred when the tension on the rope dislodged the fused portion from the bitts. Since the rope 11, however, consists predominantly of polypropylene, it will possess all of the advantages of that material, i.e., lightness, buoyancy, water-resistance, great tensile strength, low elongation, and stability even at very low temperatures. Very good results were obtained by using the isotactic monolamentary polypropylene sold by Hercules Powder Company under the trademark designation Pro-Fax 6514.
For best results the nylon constituent of the outer layer of each of the strands and/or the core material of the composite rope 11 is impregnated or treated with a lubricant which enhances its natural water-repellency, reduces friction and hence reduces the heat generated 'by the ropes passage ove1 the surface of the bitts, and tends to prevent wear of the rope. Many cordage lubricants tend to wash out as soon as the rope is subjected to immersion in water, or work out of the rope when it is twisted, or decompose yat high temperatures, or become brittle at low temperatures. I have found that a certain lubricant, to be described below, does not possess these disadvantages and also is not injurious to workers handling the rope.
This special lubricant has as its principal ingredients a napthenic or parafnic oil, such as a light cordage oil, a suspension of mica, and a suspending agent consisting of certain cation exchange reaction products between organic bases and bentonite. The oil, ground mica, and bentonite derivative constitute 70%, 20% and 10% (by weight) respectively of the lubricant. One light cordage oil which has proved eminently successful consists of Naprex 908 available commercially from the Mobil Oil Company. The ground mica may be #325 mesh white waterground mica such as can be obtained from the Witco Chemical Company of New York. The bentonite derivative may be Bentone 34 sold by The National Lead Company.
If it is desired to treat just the nylon yarns one may apply this special lubricant either to individual `filaments of the nylon or to the nylon yarn. The former method consists of stretching the nylon filaments while still hot between two Godet rollers, one of which turns much faster than the other, for orienting the molecules of the filamentary material. The stretched iilaments are then passed over a contact or kiss roller which is partially immersed in the special lubricant which is at room temperature. A knife blade control may make contact with the surface of the roller Ito wipe olf the excess lubricant thereby controlling the amount and evenness of the deposition of the lubricant on'the filaments. The amount of the lubricant may be from about 5% to 15% by weight of the nylon, 8%*10% being a preferred range.
If the lubricating mixture is applied to the yarn itself, a number of twisted filaments are passed through a bath of the lubricant at room temperature and then through a set of squeeze rollers to remove the `excess solution.
The amount deposited may be in the same range by weight as the lubricant when it is applied to the individual filaments of nylon.
By impregnating the nylon or other selected yarns With this preferred lubricant, the resultant rope has a greater translation efficiency. The latter term refers to the ratio of the strength of the rope when it is twisted together to the strength of its components before twisting, there being a loss in strength in the twisting process. This twisting loss occurs because the tilaments rub against and abrade one another and because the twisting itself introduces strains into the rope as a whole. The action of the special lubricant is to reduce the inter-iilamentary friction thereby increasing the translation eiciency. rThe lubricant also reduces undesired high temperature eifects on the rope which may be caused by friction of the rope with other surfaces. This special lubricant is especially tenacious and does not easily wash out of the rope when immersed in water nor does it Work out due to twisting or squeezing of the rope.
The rope 111 is only slightly heavier than a rope made of pure polypropylene, but in any case it is buoyant since it has a specific gravity of less than one.
While the invention has been explained in terms of a rope having a core material composed of polypropylene, Yit is also applicable to ropes having other combinations of synthetic libres. For example, polyethylene of the low pressure, high tenacity type can be used as it is about 75% stronger (tensile strength) and 35% lighter than ordinary rope made of natural fibres. Since the melting point for this kind of polyethylene is around 270 F., it is evident that the problem of sticking or -grabbing onto the bitts is even more likely to arise. Hence, if the core material and part of the outer layer is polyethylene, the action of the treated nylon yarns in the outer layer will electively prevent adhesion of the rope to the bitts.
In the place of nylon, it is also possible to use a polyester iibre whose melting point is approximately the same as that of nylon and hence would resist sticking to the bitts; It is likewise possible to use cellulosic iibres like 'rayon (which is extremely resistant to high temperatures) instead of nylon, or synthetic materials derived from polyvinyl alcohol which are stronger than polyester fabrics but have a somewhat lower melting point than nylon.
One can see that many combinations of the synthetic plastic materials may be employed within the scope of the present invention depending upon the application desired without departing from the essence of the present invention.
l. A synthetic rope comprising: a selected number of strands, selected ones of said strands having a core which includes selected synthetic thermoplastic materials whose melting point temperatures fall within a first predetermined range, and at least one layer surrounding said core which includes a plurality of yarns of selected ones of said thermoplastic materials and also includes a plurality of yarns of selected other synthetic materials whose respective melting point temperatures fall within asecond predetermined range which is substantially higher than said rst range.
2. A synthetic rope comprising: a plurality of strands each having a core which includes selected synthetic thermoplastic materials and at least one layer of yarns surrounding said core, said layer including a plurality of yarns of selected ones of said core materials and also including a plurality of yarns of selected other synthetic materials having a substantially higher resistance to elevated temperatures than said core materials.
3. A synthetic rope comprising: a plurality of strands each having a core composed principally of yarns made .from a polymer of olenic hydrocarbons from the class consisting of polypropylene and polyethylene and an outer layer of yarns surrounding said core, said layer including a plurality of yarns of selected ones of said core materims, said layer also including a plurality of yarns of selected other synthetic materials which are substantially more resistant to elevated temperatures than said core materials.
4. A synthetic rope according to claim 3 wherein said other synthetic materials are from the class consisting of nylon and polyester iibres.
5. A synthetic rope comprising: a plurality of strands each having a core of a material comprising a polymer of oletinic hydrocarbons from the class of synthetic materials consisting of polypropylene and polyethylene and a layer of yarns surrounding said core, said layer including a plurality of yarns made of materials from said class of core materials interspersed with a plurality of yarns from the class of synthetic materials which consists of nylon and polyester bres.
6. A synthetic rope comprising: a plurality of strands each having a core composed principally of polypropylene yarns surrounded by an outer layer which includes a plurality of yarns of polypropylene interspersed with a plurality of yarns of nylon.
7. A synthetic rope comprising: a plurality of strands each having a core consisting principally of a plurality ot isotactic polypropylene yarns surrounded by an outer layer which comprises a plurality of yarns of said polypropylene interspersed with a plurality of yarns of nylon.
8. A synthetic rope comprising: a plurality of strands each having a core principally of isotactic mono-filamentary polypropylene surrounded by an outer layer having a plurality of yarns of said polypropylene interspersed with a plurality of yarns of a lubricated nylon.
9. A synthetic rope comprising: a plurality of strands each having a core consisting principally of a plurality of isotactic mono-ilamentary polypropylene yarns surrounded by an outer layer which includes a plurality of yarns of said polypropylene alternately interspersed with a plurality of yarns of nylon.
10. A synthetic rope according to claim 9 wherein selected ones of said yarns in said outer layer are lubricated.
11. A synthetic rope according to claim lO wherein said lubricant constitutes tive to fteen percent by weight of the selected yarns to which it is applied.
12. A synthetic rope according to claim 10 wherein said lubricant constitutes 8%-10% by weight of the selected yarns to which it is applied.
13. A rope comprising: a plurality of strands, each having a core which includes selected thermoplastic materials whose melting point temperatures fall within a rst predetermined range, and an outer layer surrounding said core which includes selected thermoplastic materials having melting point temperatures within said first range and selected other materials whose melting point temperatures fall within a second predetermined range which is substantially higher than said first range.
14. A strand for an essentially synthetic rope comprising: a core which includes selected thermoplastic materials whose melting point temperatures fall within a irst predetermined range, and an outer layer surrounding said core which includes selected thermoplastic materials having melting point temperatures within said rst range and selected other materials Whose melting point temperatures fall within a second predetermined range which is substantially higher than said rst range.
References Cited in the le of this patent UNITED STATES PATENTS 2,917,891 Murdock Dec. 22, 1959 2,999,413 Momoi Sept. 12, 1961 2,000,171 Swanser Sept. 19, 1961 FOREIGN PATENTS 538,782 Belgium Dec. 6, 1955 833,387 Great Britain Apr. 21, 1960